The common cold is a benign disease that also causes ear infections in children and is a leading cause of "attacks" in asthmatic patients. Common cold infections have a great economic impact but are currently treated by OTC remedies intended to alleviate symptoms. Human rhinoviruses cause 70 percent of colds and include >120 different serotypes. This large genetic diversity makes development of a vaccine near impossible. However, about 90 percent of rhinovirus serotypes bind to nasal epithelial cell surface receptor, ICAM- 1. We have developed prototype anti-ICAM-1 antibody fusion constructs that bind to ICAM-1 with high affinity and that prevent rhinovirus infection in cell culture assays. High affinity (low Koff) antibodies are essential for durable protection from infection. This proposal describes a novel method for in vitro affinity enhancement of the antibody through selective amino acid substitutions. The choice of residues to mutate is critical for efficiency and success. Amino acid residues are mutated individually and together to generate E. coli based libraries. Libraries are screened using an "off rate" screening method designed to select for specific, high affinity (low Koff) binding. Once the core antibody has been affinity enhanced, it will be used to generate fusion constructs for clinical evaluation. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE